1. Field of the Invention
The present invention generally relates to an apparatus for scanning objects of various types, and more particularly to a scanner which can compensate for optical characteristics according to using different wavelength light sources.
2. Description of the Prior Art
Optical scanning apparatuses are currently in great demand as a result of the rapid development of high speed, low cost imaging devices and the ever decreasing cost of personal computers. Optical scanners, in general, are capable of reflective and/or transmissive scanning of documents, photographs and the like, whereby reflective scanning is used with opaque objects such as photographs and transmissive scanning is used with transparent objects, such as slides and the like. Reflective scanners project light onto the side of the object to be scanned. The reflected light is viewed by an optical sensor which converts the reflected light into digital code. The code is then transmitted to the operator's computer for further processing. Transmissive scanners operate on the same principle except that light is projected through the transparent object being scanned. A great demand exists for high quality, low cost, low maintenance, easy to calibrate, versatile optical scanners capable of both high and low resolution reflective and transmissive scanning.
As shown on FIG. 1, a conventional scanner typically comprises a control module 110, a light source 111, a power module 112, a image capture module 113, a loading platform module 114, and a translation module 115. The control module 110 comprises a host unit for image processing and a plurality of control circuits for scanning process. The light source 111 is for use while an object is scanned. The power module 112 comprises power units for supporting scanning process. The image capture module 113 comprises a plurality of lenses and optical sensors. The lenses are for performing optical pathways and the optical sensors, such as charge-coupled devices, are for sensing lights from the lenses and convert light signals into electric signals. A translation module is for translating the light source 111 and the image capture module in a main-scanning direction when the object is scanned.
Generally, there are many different types for scanned objects, such as paper document, transparent slide, and so on. A high-quality output image depends on the imaging system of a scanner for different types of objects. However, there are many factors related to the good imaging system, such as wavelength of light source, optical characteristics of optical devices and optical pathway, and so on. That is, the high-quality output images can't be satisfied for objects of various types if there is only one imaging system in a scanner.